Blood pump with splitter impeller blades and splitter stator vanes and related methods

Abstract

A rotordynamic pump for delivering continuous flow of fluids, such as blood, is provided. In one embodiment, the pump includes a stator housing having an inlet and an outlet. A rotor hub is disposed within the stator housing having a mixed-stage or mixed-flow impeller. The mixed flow impeller includes both principle blades and splitter blades, the splitter blades exhibiting a shorter axial length than the principle blades. One or more stator vanes and extend radially inwardly from the stator housing. The splitter blades and principle blades are arranged in a circumferentially alternating pattern. The stator vanes include principle stator vanes and splitter stator vanes, the splitter stator vanes exhibiting a shorter axial length than the principle stator vanes. The splitter vanes and principle vanes are arranged in a circumferentially alternating pattern. The rotor hub may be magnetically suspended and rotated within the stator housing.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application claims priority to U.S. Provisional Patent Application No. 61 / 394,220, filed Oct. 18, 2010, and entitled BLOOD PUMP WITH SPLITTER IMPELLER BLADES AND SPLITTER STATOR BLADES. This application also claims priority to U.S. Provisional Patent Application No. 61 / 394,213 filed Oct. 18, 2010, entitled BLOOD PUMP WITH SEPARATE MIXED-FLOW AND AXIAL FLOW IMPELLER STAGES. The disclosures of the above referenced priority applications are incorporated by reference herein in their entireties.TECHNICAL FIELD[0002]This invention relates generally to pumps. More specifically, this invention relates to blood pumps, such as cardiac assist pumps that may be implanted in a patient.BACKGROUND OF THE INVENTION[0003]Rotordynamic pumps, such as centrifugal, mixed-flow, and axial-flow pumps with mechanical bearings or magnetically suspended systems, have been widely used as ventricular assist devices to support patients with heart diseases. In mag...

AI Technical Summary

Benefits of technology

[0018]In various exemplary embodiments, there may be provided a rotordynamic apparatus and method suitable long-term implantation into humans for artificial circulatory support. In one embodiment, there may be provided a rotordynamic blood pump and method including a flow path geometry characterized with high hydraulic efficiency, low power consumption, uniform flow fields, smooth operation, and low blood damage at both nominal flow and off-design conditions.

[0019]In another embodiment, there may be provided a rotordynamic blood pump suitable for easy arrangements of magnetic suspension and drive components along the annular portion of the flow path.

[0021]High efficiency, low blood damage, and smooth operation at design and off-design conditions are the critical requirements for a long term implantable blood pump. High efficiency is accomplished with the inclusion of splitter blades for both impeller and stator. The leading edges of both the impeller and stator shorter splitter blades are staggered with respect to principle blades, and initiate subsequently to the leading edge of the principle blades and overlap a portion of the principle blades wherein both principle and splitter blades preferably terminate at the same position in meridional section. Such an arrangement lessens the flow blockage at the impeller inlet side, thus improving the uniformity of flow field at the impeller inlet region by preventing undesirable flow patterns such as the pre-rotation, retrograde flow, and inlet circulation from occurrence at the design and off-design conditions. Because splitter blades take some percentage of pressure loading from the principle blades, it makes the pressure distribution more uniform along the entire blade region and especially on the outlet side of the impeller blades and stator blades at all operating conditions. Therefore, the flow at the outlets of the impeller and stator blades becomes difficult to separate. Outflow circulation and vortices are further prevented from occurrence. All these improvements in flow field and pressure distribution result in an increased pump efficiency. The higher efficiency provides the benefit of low temperature rise of the motor and longer battery life. As contact with bodily tissues is inherent, the reduction in operating temperatures minimizes related trauma to surrounding body tissues.

[0022]Red blood cell damage in blood pumps is mainly related to the shear stress and exposure time of the red blood cells passing through the flow paths. A uniform flow field without separation and vortices due to the consideration of splitter blades leads to a low shear stress and short exposure time. Among other things, embodiments of the present invention device address such issues. Embodiments of the present invention further provide smooth operation at design and off-design conditions because the configuration of the splitter blades fitted into the impeller and stator can, to a great extent, prevent from occurrence of undesirable steady and unsteady flow patterns such as the separation, inlet pre-rotation, retrograde flow, inlet and outlet circulation, and surge as well.

Problems solved by technology

One adverse outcome of operating a rotor at high rotational speeds is a tendency for high turbulence flow characteristics within the blood (e.g., high shear stress) that increase the extent and rate of red blood cell damage.

This is a challenge in developing a long-term implantable ventricular assist device.

Additionally, for centrifugal or mixed-flow blood pumps with shrouded impellers (i.e., a circumferentially revolved surface interconnecting the impeller blade tips), the fluid within the clearance space between a rotating front shroud and the stationary housing can demonstrate a complex three-dimensional structure, leading to retrograde leakage flow and strong disk friction loss.

The combination of disk friction loss and the strong vortical flow not only lowers pump efficiency but also potentially induces hemolysis and thrombosis.

For centrifugal or mixed-flow blood pumps with unshrouded or semi-open impellers, the lack of a front shroud introduces a problem due to the blade tip leakage flow from pressure-side to suction-side of the blades which occurs through the clearance between the rotating blade tip and the stationary housing.

The leakage flow can also generate a jet leakage vortex that interacts with the primary flow, causing hydraulic loss and possibly inducing blood trauma.

At some off-design conditions, undesirable flow patterns such as flow separation, vortices, retrograde flow, and inlet pre-rotation can occur in all types of rotordynamic pumps.

All these undesirable flow patterns not only cause hydraulic losses, but may also induce hemolysis and thrombosis.

At some other off-design conditions, unsteady flow patterns such as surge can occur.

Such an unsteady flow pattern not only has a significant effect on the pump efficiency and potential blood damage, but also may have a strong impact on the stability of the pump operation.

However, undesirable steady and unsteady flow patterns such as flow separation, vortices, inlet and outlet recirculation, and surge can also occur at impeller and stator blades region at off-design conditions.

In particular at some off-design condition such as high flow rate operation, an unsteady surge can cause unstable operation of the pump.

Images